Contributed by John Zagar
Edited by Jo Gardner

A feed unit is more than just an  automatic drill press. It is an automated, self-contained, modular machining unit usually offering two axis of motion-spindle rotation and linear feed.  Feed Units can do everything  from drilling and tapping to drill/reaming.  A carefully selected, and optimized feed unit can offer a rich payoff.  Unfortunately, it is also easy to end up with a poorly applied feed unit, a slow production rate and frustrated machinists.

In the 1st installment, we covered general variables in mechanical feed unit selection.  Mechanical, hydraulic, and pneumatic feed units each have different features and functions that perform best when used for certain applications. 

In the 2nd Installment, we covered mechanical feed units including: ballscrew units, cam feed units and gear units.

The 3rd installment covered Pneumatic and Hydraulic feed units, as well as requirements to take into consideration in Feed Unit selection.  Our final installment today covers other considerations such as setup, flexibility, precision, and more.

Other Feed Unit Selection Considerations.

Additional considerations in feed unit selection are ease of setup, flexibility, precision, power-supply needs, and your plant’s specific production methods.

If the unit is to be used for a long run dedicated job, ease of setup should not be a major priority. If, however, the unit is to be used in situations involving frequent part changeovers, a ballscrew feed unit will serve you best, since its programmability facilitates more easy transitions to new applications.

A feed unit’s flexibility can be measured in terms of its programming capability or ease of setup. Will the unit need to perform a variety of tasks, and do these tasks fail to fit into a canned or preprogrammed setup? If so, flexibility is a key feature to look for. Also, determine unit setup time in terms of opera­tor instruction time.

It’s also important to determine how accurate hole features must be and whether the unit you are considering provides more accuracy than you need to pay for, less accuracy than you require, or the degree of accuracy that’s right for the job. Often, it’s up to the feed-unit manufacturer to determine whether or not a particular unit can meet a customer’s hole tolerances on position and size. Often, customers send requirements to the feed-unit manufacturer for them to determine the best suited unit. The more you know about feed units, the less you’ll have to depend on the manufacturer’s judgment.

Once you decide on a specific feed unit, you must also evaluate your existing power supplies, regardless of whether the unit is mechanical, hydraulic, or pneumatic. Being consistent with your current power supply and choosing the most energy efficient source will save you the largest amount of money in the end.

Your plant’s specific production methods also will determine what feed unit is best. If it’s for just-in-time delivery that requires an increased part turnover rate and low inventory, you should look for a feed unit that requires little or no downtime. Units with wear parts subjected to frictional loads and high maintenance units typically have more downtime associated with them. However, the ballscrew in a ballscrew feed unit, when properly designed, encounters only rolling friction (the lowest kind of friction). Therefore, it can reduce the need for replacement parts and offer longer between-service times.

Feed-Unit Options

Zagar’s optional feed-unit features allow you to customize your purchase to meet your company’s needs and we can provide you with all the bells and whistles you may not expect. Our feed unit options include various styles of multispindle drilling and tapping heads, toolholders, controls, motors, speed kits, through-coolant capability, and even programming services. Zagar Drill and tap heads come in various shapes and sizes as well.

Sometimes Toolholders are required to attach the tool. If a manufacturer does not have an integral spindle-nose option to attach a specific tool to the feed unit, then the customer needs to be aware of the toolholder options available from that manufacturer.

With standard control options for feed units, it is important to determine which standard controls are offered, whether or not they are sufficient, and whether or not additional controls are required.

Motors are usually standardized as well. Ask yourself: Is the standard acceptable, or do I need more power and speed from the motor? Manipulating fixed speed, as in a pneumatic unit, requires changing belts and pulleys and can be labor inten­sive if the changeover is complex. A programmable ballscrew unit, however, can be preprogrammed.  Parameters can be changed easily with an operator interface.

The through-coolant option allows coolant to be passed through the tool in two ways. The coolant can be provided either through a rotary union passing coolant through the center of the unit, or through a front-end gland on the spindle nose.

Custom programming service options allow customers to identify their parts with their terminology or specialize a program to meet their needs. The controls become familiar to operators, because they can understand the operations or data entry conventions with a minimal learning curve.

Among the many production pluses gained from incorporating a feed unit into your manufacturing process, feed units offer other less obvious benefits. Their modular construction can be easily adapted to new machinery with minimal setup time. With programmable units, part changeover time is rapid.

Feed units can enhance machining efficiency. Secondary operations, which burden most CNC machines, are taken offline, and previously labor-intensive procedures become seamlessly automated.

Engineers, machinists, purchasers and manufacturers can choose from many feed units and feed unit options.  Because there is no single unit that is best for an entire industry, it is critical to first understand your buying needs, then tailor your purchase for the best results in your application.  Remember, when you need to choose a system and tooling supplier; lZagar Inc. is here for you with solid advice, excellent technical support and service, and a wide variety of feed unit features available to suit your needs.